Abstract: Utilizing the classical earth pressure theory for setting the reasonable thrust line position of soil slice, the linear equations including as variable are established by the condition of static equilibrium and torque equilibrium, where is safety factor of slice side. Least square method is applied to solving the above linear equations by means of MATLAB program based on the maximum principle and reasonable conditions: . Case studies show that the capacity for resisting shear deformation of slope is brought into play when The slope safety factor decreases with thrust line position increasing; but the impact of thrust on slope safety factor is negligible. The safety factor obtained by the above method is little larger than those by other methods.

Key words: least squares method, stability analysis of slope, linear equations